Would my engine cope?

[Tryweryn]

Hi would a engine like this in a Moody 30 cope with a journey of 200 miles or are these engines just small and for getting into and out of harbors etc? ie can u cruise long distance under power with such? Many thanks.

Engine Brand: Beta Marine 3 cyl' 20hp
Year Built: 2005
Engine Type: Inboard
Engine/Fuel Type: Diesel
Propeller: 3 blade propeller
Drive Type: Direct Drive
Engine(s) Total Power: 20 HP

 

[sailorman]

They run in diggers all day long week in week out, 6k hrs trouble free just service as schedule

 

[prv]

Hi would a engine like this in a Moody 30 cope with a journey of 200 miles

Yes, you certainly could motor that distance (fuel tank permitting), but it would be more pleasant to sail as much of it as possible. Less noise, more fun, nicer motion.

Learn a lot more before you set out on such a trip though

Pete

 

[john_morris_uk]

You've had the answer (which is a resounding yes, of course it will motor for 200 miles) but even if the wind is in not quite the right direction motoring with the main up and sheeted hard in and just pulling is MUCH nicer than motoring and rolling around in any swell that there is.

However if the wind is aft enough, why not sail?

I can see why someone in a hurry might motor sail the windward bit, but it will save you a few bob in fuel is you put the white rags up as soon as you've got a free enough wind.

 

[Tryweryn]

Many thanks. I agree sailing is the fun part. I was curious if the engine could cope as most cruiser/sail seem to have engines twice the size. It's nice to know it's not something from a sewing machine lol

 

[sailorman]

my Co32 has a single pot 12hp donk

 

[Tryweryn]

Out of curiosity whats your cruising speed?

 

[sailorman]

Out of curiosity whats your cruising speed?

present boat 7kts
your Moody probably 5.5 >6 kts

 

[Tranona]

Many thanks. I agree sailing is the fun part. I was curious if the engine could cope as most cruiser/sail seem to have engines twice the size. It's nice to know it's not something from a sewing machine lol

That is the correct size of engine for the boat. It is the propeller that moves the boat and the engine just needs enough power to turn the prop. The speed of the boat is limited by its waterline length so the installer of the engine will have chosen the appropriate combination of engine and propeller to achieve the maximum hull speed at full revs. Obviously at cruising speed you run the engine at lower revs, normally at around 75% maximum power. Many boats are over powered in the vain hope that they will go faster. As already suggested your Kubota base engine is designed to run industrial equipment with a life of 8000 hours, so the 40 or 50 hours to do 200 miles is nothing.

 

[Tryweryn]

Thats interesting as this engine will only cruise the moody 30 at 5 and 7knots max.

 

[sailorman]

Thats interesting as this engine will only cruise the moody 30 at 5 and 7knots max.

I doubt you will be able to attain 7kts

 

[Tryweryn]

@Tranona that all makes sense.Do these folding propellers make a difference?

 

[Tryweryn]

@sailorman ah is that under amazing conditions like car mileage lol

 

[Tryweryn]

I assume a moody 30 is a plodder lol more a white van than a MG?

 

[Tranona]

Thats interesting as this engine will only cruise the moody 30 at 5 and 7knots max.

See my previous post. The maximum displacement speed of your hull is calculated as approx 1.4*sq root of waterline length which gives you around 6.5 knots in flat water. No matter how much extra power you put in you will not go significantly faster. Your cruising speed will be just over 5 knots, but you may not be able to maintain this against big seas and strong wind. These are just facts of life, so you need to consider them when making your passage plans. In particular around the coast making maximum use of favourable tides.

Folding propellers are often less good than fixed propellers, particularly in adverse conditions. Their big advantage is reduction in drag under sail leading to speed increases, particularly in light airs.

 

[Tryweryn]

So the max speed is determined by the wave created by the boat itself?

 

[Tryweryn]

Many thanks u pick up loads of good info in such threads many thanks.

 

[prv]

So the max speed is determined by the wave created by the boat itself?

I've never heard it said like that before, but it does sound right in a way

So do you own this Moody, or is it something you're thinking of buying?

Pete

 

[Tryweryn]

From my physics i remember something about the object passing through a liquid creates a wave that it has to overcome and reaches a stage where it slips back .....something like that. Well surveyors just doing his work now but it seems ok just needs a damn good clean. Was after a 33 but the 30 is big enough. I'm curiouse if with more experience i could get a moody 30 to say the Faroe Isles. Looked at that many boats over the months of all types.

 

[Lakesailor]

So the max speed is determined by the wave created by the boat itself?

In this pic the boat is doing 5 knots. It's a 15ft boat and you can see it's trying to climb over it's own bow wave, but the stern has sunk into it's own trough. In fact, the more the bow lifts, the shorter the waterline length.So it's pretty much self-limiting.
That's a 5 hp motor. I doubt a 20hp would have made any difference. Apart from noise and vibration.

After I fitted remotes and could sit further forward it would achieve 5.5 knots.